Lacto-N-biose I (Galβ1-3GlcNAc) and galacto-N-biose (Galβ1-3GalNAc), which are β1,3-galactosides, have structures often seen in physiologically active sugar chains. They can be applied as functional sugar and the like in food industries and can also be used as pharmaceutical preparations or reagents, such as substrates or inhibitors of enzymes or lectins, and constituent sugars of living bodies.
Examples of a conventionally known method for producing these compounds include a method for producing lacto-N-biose I (JP Patent Publication (Kokai) No. H06-253878 A (1994)), which is characterized by sequentially reacting a substrate containing lactose and N-acetylglucosamine as a starting material with β-galactosidase derived from porcine testis and β-galactosidase produced by Bacillus circulans, and a method for producing complex carbohydrates (JP Patent Publication (Kokai) No. 2003-189891 A) using microorganisms, animal cells, or insect cells capable of producing complex carbohydrates from sugar nucleotides and complex carbohydrate precursors. However, the former method exerts low reaction efficiency and the latter method is a method for producing such sugar using a fermentation method. Hence, both methods lack practicality in that production of the compounds always creates rising costs.
JP Patent Publication (Kokai) No. 2005-341883 A suggests that a lacto-N-biose derivative can be synthesized using the reverse reaction catalytic activity of lacto-N-biose phosphorylase, and galactose-1-phosphate as a raw material. However, galactose-1-phosphate is expensive, and thus the method lacks practical value.